Nicnic:
If you don't get any other responses in here, you might try these people:
http://www.kissler.com/
Kissler sells new plumbing repair parts, but they also sell plumbing parts that are no longer available from the original manufacturer. Kissler simply buys those obsolete parts from the same companies in China, Malaysia or Mexico that produced them for the original manufacturers. Kissler also has their own in-house machine shop where they make bronze and brass plumbing repair parts that aren't available from anyone anymore.
Kissler has a $250 minimum order, so you won't be buying directly from them. Just phone them up and ask to talk to anyone in billing who can tell you which companies in your area order from Kissler on a regular basis, and then just order through them.
I have Crane Tub & Shower faucets in all of my bathrooms. Crane decided to discontinue manufacturing that faucet in the 90's, and the escutcheon plates that fit around the hot and cold water knobs were no longer available for that faucet after about 2000. Just two years ago I bought 30 of them from a hardware store chain in Minnesota called "Handymans" who ordered them from Kissler who still purchase them from the original manufacturer in Taiwan.